the cell membrane, diffusion, osmosis, and active transport 2011-2012

8/3/2019 The Cell Membrane, Diffusion, Osmosis, And Active Transport 2011-2012

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The Cell Membrane,Diffusion, Osmosis, andActive Transport


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Definitions Diffusion

Concentration

Semi-permeable Solution

Solute

Solvent


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Solution:

Usually a liquid mixture of two or more

substances that are evenly distributed atthe molecular level.

It is usually (but not always) made of a

liquid that dissolves one or more solids.

Solvent: The liquid part of the solution

Solute: The solid part of the solution


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The Cell Membrane Allcells are surrounded by a cell membrane.

It separates the contents of the cell from itsenvironment, regulates the passage of

molecules into and out of the cell, and it allowsthe cell to communicate and interact with other

cells.

Because the cell membrane regulates what canenter and what can leave the cell, it is called a

selectively permeable membrane.


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What substances do youthink a cell needs toimport (bring in) and/orexport (send out)?


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Yes, ________ you are right

Imports : Water, Gasses,Sources of Energy,Nutrients, etc

Exports :* Waste Materialsand materials other cells

may need.


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Structure of Cell Membrane

All cell membranes contain two layers of

molecules called phospholipids.

Hence the name Phospholipid Bilayer


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Diffusion Diffusion is the process of substances moving

from a higher concentration to a lowerconcentration.

Diffusion does not need energy for it tooccur.

If a substance is found at a higherconcentration out-side the cell and canmovethrough the cell membrane freely, it will moveinto the cell.


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What would happen if a substanceis found at a higher concentration

inside the cell than outside the cell,and can move through the cell

membrane freely?


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Yes, ________ that is correct.The molecules would move from theinside of the cell to outside the cell by

diffusion.


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Osmosis

Osmosis is the movement of watermolecules across a membranefrom ahigher concentration of water to a

lower concentration of water.

Osmosis does not need energy to

occur.


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Effect of Osmosis on Cells


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Active transport

Active transport involves the movement ofsubstances from a lower concentration to ahigher concentration.

Active transport needsenergy to occur.

The cell has special transport proteins in thecell membrane that transports substances in orout of the cell.


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Diffusion of LargerMolecules Larger molecules like sugars, starches, and

proteins sometimes diffuse through proteinchannels.

Because the molecules move from greater tolesser concentration through the channels,

this process also does not require energy.


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Engulfing A cell can take in larger particles of food by

engulfing them. The cell membrane forms apocket around the particle. Once inside the cell,the pocket breaks loose from the cell

membrane.

Cells also send material out of the cell in the

same way.

Both of these processes are types of active

transport because they require energy.


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the cell membrane, diffusion, osmosis, and active transport 2011-2012

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